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/* taylor.c */

/* Jonathan P Dawson */

/* 2013-12-23 */

/* globals */

float pi=3.14159265359;

/* approximate the cosine function using Taylor series */

float taylor(float angle){

    float old, approximation, sign, power, fact;

    unsigned count, i;

    approximation = 1.0;

    old = 0.0;

    sign = -1.0;

    count = 1;

    power = 1.0;

    fact = 1.0;

    for(i=2; approximation!=old; i+=2){

        old = approximation;

        while(count<=i){

            power*=angle;

            fact*=count;

            count++;

        }

        approximation += sign*(power/fact);

        sign = -sign;

    }

    return approximation;

}

/* return the cosine of angle in radians */

float cos(float angle){

    return taylor(angle);

}

/* return the sine of angle in radians */

float sin(float angle){

    return cos(angle-(pi/2));

}

/* test routine */

void main(){

    float x;

    float step=pi/25;

    for(x=-2*pi; x <= 2*pi; x += step){

       file_write(x, "x");

       file_write(cos(x), "cos_x");

       file_write(sin(x), "sin_x");

    }

}